1. Field of the Invention
The present invention relates to a rotary mimeographic printing apparatus in which a perforated stencil is mounted on and removed from a rotary drum automatically.
2. Description of the Related Art
In a rotary mimeographic printing apparatus in which a perforated stencil is mounted on and around a peripheral surface of a rotary drum, a high degree of reliability is require in supplying and mounting the stencil onto the drum and also in removing and discharging the stencil from the drum.
To this end, an automatic mimeographic printing apparatus, in which perforating of a stencil, mounting of the perforated stencil, printing, and discharging of the stencil can be performed automatically, was proposed by commonly assigned Japanese Patent Laid-Open Publication No. 224573/1985 (Japanese Patent Application No. 80846/1984).
In this prior apparatus, as shown in FIG. 15 of the accompanying drawings, a clamp 103 is pivotally supported on a peripheral surface of a rotary drum 101 and clamps one end of a perforated stencil 102 supplied to the rotary drum 101. With its one end held by the clamp 103, the stencil 102 is wound around the peripheral surface of the rotary drum 101 as the rotary drum 101 is rotated. At that time the stencil 102 is attached to the peripheral surface of the rotary drum 101 by adhesion of a printing ink applied to the drum surface from the inner side of the rotary drum 101.
Upstream of the rotary drum 101, a stencil conveying means (not shown) and a cutter 104 are disposed, and downstream of the rotary drum 101, discharge rollers 105 are disposed for removing and discharging the stencil 102 from the rotary drum 101. At a position above the rotary drum 101 and between the cutter 104 and the discharge rollers 105, a guide 106 is disposed for guiding the leading end of the perforated stencil 102, which tends to be curled. In the printing apparatus of this type, since the individual stencil 102 of a suitable length to be supplied to the rotary drum 101 is provided from a roll of a stencil by cutting by the cutter 104, the stencil 102 would often assume a curled posture. If the leading end of the stencil 102 which is conveyed toward or released from the clamp 103 is curled in the direction away from the peripheral surface of the drum 101, such curled end of the stencil 102 is guided by the guide 106.
The guide 106 is in the form of a pair of plates disposed above outer ends of the clamp 103 so as not to impede pivotal movement of the clamp 103. Therefore, if the stencil 102 is curled remarkably, the central portion, which is free from any contact with the guide plates, of the stencil 102 would be deformed to a large extent, compared with the opposite marginal portions, which are guided by the guide 106 in contact with the respective guide plates. As a result, the stencil 102 would occasionally be slipped out upwardly of the guide plates, as indicated in phantom lines in FIG. 15. This phenomenon would occur not only when mounting the stencil 102 onto the drum 101 but also when discharging the stencil 102 from the drum 101.